Does anyone know how to differentiate 68-72 German rear fender from
aftermarket?

Here are some qualities I have noticed while walking around the junkyard:

Extra bolt hole in the front.
Water drain holes in the rear lip.
Some fenders have square or rounded tabs around some of the bolt holes.
Some aftermarket fenders have obviously not been painted or well undercoated
are are surface rusted underneath.
Some are lightweight and flimsly and obviously aftermarket.

Let me know what to look for to positively I.D. as German.
Thanks!